Liquid rheostat.



A. J. HALL.

LIQUID RHEOSTA'T.

APPLICATION FILED FEB. 12. 1915.

1,275,908. Patented Aug. 13, 191s.

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UNITED STATES PATENT curios.

ARTHUR J'..HALL, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR 'IO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

LIQUID nHEosTAr.

Specification of Letters Patent.

Application filed February 17, 1915. Serial No. 8,870.

To all whom it may concern:

Be it known that I, ARTHUR J. HALL, a subject of theKing of Great Britain, and a resident of filkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Liquid Rheostats, of which the following is a specification.

My invention relates to liquid rheostats, and it has special reference to liquid rheostats that are employed for the purpose of governing the acceleration of railwaypolyphase induction motors or the like.

One of the objects of my invention is to provide simple, reliable and effective means for automatically replacing the losses due to the evaporation of the electrolyte within 1 the rheostat and maintaining a substantially constant amount of electrolyte which may be continuously circulated through the liquid rheostat for the purpose of dissipating the heat developed therein.

Another object of my invention is to provide automatic means for maintaining the density of solution of the electrolyte at a substantially constant value, whereby the functioning of the rheostat, with respect to the motor which it is adapted to govern, is uniform at all times.

In the prior art, it has been common to provide means for effecting a continuous circulation of an electrolyte comprising a solution of sodium carbonate and water through a liquid rheostat, and under normal conditions, it has been found desirable to employ a solution including approximately .7 5% of sodium carbonate. However, under operating conditions, particularly for heavy service, where the heat developed in the rheostat is great, a material amount of water in the solution ,is lost by reason of excessive evaporation. Therefore, the volume of electrolyte is reduced in amount, and, moreover, the solution gradually be comes more concentrated. Consequently the effect of the rheostat upon the motor which it governs is materially modified.

For instance, it has been determined that, when the electrolyte solution becomes concentrated to approximately 1.5% of sodium carbonate, the initial immersion of the rheostat electrodes causes a very decided olt and shock to the apparatus which is objectionable and, moreover, interferes with its normal operation.

According to my invention, I provide an auxiliary tank of relatively fresh water which shall be so located and connected to a main electrolyte-containing reservoir as to automatically supply water to the body of electrolyte whenever the volume has de- Patented Aug.'13, 1918.

creased to a predetermined amount. In so 1 doing, the volume is maintained substantially constant, while, at the same time, the added fresh water serves to dilute the so lution and to prevent undue concentration thereof which would otherwise result by reason of the loss due to evaporation.

beneath said rheostat, a pump 3 for circulating the electrolyte continuously through the rheostat and the reservoir, and an auxiliary fresh-water-containing tank 4 that is elevated above the main reservoir 2 and is adapted to deliver fresh water to the body of electrolyte in accordance with predetermined conditions. I y r The liquid rheostat 1 may be of any suitable type of construction that is adapted for a continuous circulation of electrolyte, although I prefer a form of rheostat embodying a tank 6 having a bottom opening 7 in which is disposed a movable combined discharge and regulating valve 8 that is adapted to be raised and lowered in position for the purpose of openin and closing the discharge opening 7 an regulating the height of the electrolyte within the tank 6.

The valve 8 is tubular in form, with open top and bottom, and comprises a lower portion 9 of a diameter just sufficient to pass through the opening 7, and an upper portion 10 of smaller diameter that is adapted, in the lowest position of the valve' 8, to limit the opening 7 to an annular discharge passage through which the continuously ciroulated electrolyte which is delivered to the rheostat through an inlet opening 12, may be discharged into the reservoir 2. The tubular discharge and regulating valve 8 is suspended in position upon arod 13 that may be actuated in any suitable manner.

The rheostat 1 also embodies a plurality of sets of stationary electrodes 14.

The pump 3 pertains only indirectly to my invention and is merely illustrative of any suitable means for effecting a continuous circulation of the electrolyte contained in the reservoir 2 through the rheostat 1. For purposes of explanation, it will be assumed that the dot-and-dashlme AB, whlch is shown in the drawing as apphed to the reservoir 2, indicates the minimum level to which it is desired to permit the electroin not shown throu 'h which fresh water i may be introduced.

In order to prepare the apparatus for operation, it is first necessary to close the valve 17 and to fill the auxiliary tank 4 with fresh water through its filling opening, after which the cap 18 is replaced, and,'provided the body of electrolyte is of proper volume and density of solution, the valve 17 may be'opened.

Assuming that the volume of electrolyte is sufficient to at least maintain the minimum level AB while a continuous circulation thereof is effected through the rheostat 1 by means of the pump 3, the operation of the apparatus, so far as my invention is concerned, is as follows: To start the motor (not shown) the combined discharge and regulating valve 8 is first raised sul'hciently to close the discharge opening 7 and to cause the inflowing electrolyte to establish a socalled flush-level CD, at which the tips of the electrodes 14 are immersed. Obviously, if the upper end of the valve 8 is positioned at a heightcorresponding to the tips of the electrodes 14, the flush-level is established, and the excess of continuously supplied electrolyte overflows and is discharged through the tubular valve 8.

Those skilled in the art will understand that, as soon as the electrodes are partially immersed, the motor circuit is completed and the motor will be started into operation. The acceleration of the motor may subsequently-be governed by raising and lowering the electrolyte level within the rheostat 1 in accordance with the will of the operator.

Obviously, continuous use of a rheostat of this type, and particularly when used for governing railway motors of large capacity that are employed under severe operating conditions, the heat developed within the rheostat is very great and the evaporation of the waterin the electrolyte large. By reason of the losses by evaporation, there is a constant tendency for the solution to become concentrated which, when abnormally into the reservoir 2 until said pipe is again submerged. In this way, fresh water is automatically supplied to the system from time to time, depending upon the operating conditions, and, hence, a substantially constant volume of electrolyte is maintained, which, moreover, is of substantially uniform or constant density.

Obviously, modifications in the structural. details and arrangement and location of parts of the apparatus herein shown and de scribed may be eifected' withoutdeparting from the spirit and scope of my invention. I desire, therefore, that only such limitations shall be imposed as-are indicated in the appended claims.

I claim as my invention:

1. The combination with a liquid rheostat, a main reservoir, a body of electrolyte of a predetermined density of solution contained therein, and means for circulating said electrolyte through said rheostat, of means for automatically supplying fresh water to said electrolyte to maintain a substantially con stant density of solution, irrespective of evaporation.

2. The combination with a liquid rheostat, a main reservoir, 2. body of electrolyte of a predetermined density of solution contained therein, and means for circulating said electrolyte through said rheostat, ofmeans for supplying fresh Water to said reservoir in accordance with the evaporation.

3. The combination with a liquid rheostat, a main reservoir, a body of electrolyte contained therein, and means for circulating said electrolyte through said rheostat, of means for supplying fluid to said reservoir in accordance with the evaporation of said electrolyte.

4. The combination with a liquid rheostat, a mam reservoir, a body of'electrolyte of-a predetermined density of solution contained therein, and means-for circulating said electrolyte through said rheostat, of a fluidcontaining tank disposed above said reservoir and communicating therewith at a predetermined height and adapted to automatically maintain the level of electrolyte within said reservoir above said predetermined height.

5. The combination with a liquid rheostat. a reservoir for containing an electrolyte of a predetermined density of solution, and for circulating said electrolyte through said rheostat, of an auxiliary freshwater tank disposed above said reservoir, and a pipe communicating between said tank and said reservoir at a height substantially equal to the minimum allowable height of electrolyte within said reservoir whereby fresh water is supplied to said reservoir in accordance with the evaporation of the electrolyte to maintain a substantially fonstant density of solution of said electroyte.

6. The combination with a containing tank, and a body of electrolyte of a predetermined density of solution contained therein, of an auxiliary receptacle disposed above said tank, a body of liquid contained therein, and a pipe communicating between said receptacle and said tank at a height substantially equal to the minimum allowable height of the electrolyte within said tank whereby liquid is supplied from said receptacle whenever the electrolyte falls below a predetermined height.

In testimony whereof, I have hereunto subscribed my name this 10th day of Feb.

ARTHUR J. HALL. Witnesses H. T. MORRIS, B. B. HINES.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. 0. 

